@article{VMUMM_2011_4_a12,
     author = {A. M. Izosimov},
     title = {Smooth invariants of focus-focus singularities},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {59--61},
     publisher = {mathdoc},
     number = {4},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2011_4_a12/}
}